If $a^x=b^y=c^z=d^w$, the value of $x \bigg(\large\frac{1}{y}+\frac{1}{z}+\frac{1}{w}\bigg)$ is

Question

\[\begin {array} {1 1} (a)\;\log_a(abc) & \quad (b)\;\log_a(bcd) \\ (c)\;\log_b(cda) & \quad (d)\;\log_c(dab) \end {array}\]